1) Field of the Invention
The present invention relates to a coiled embolizing material to be deposited at an intended site in a vasculature of, for example, a human body.
2) Description of the Background Art
As a method for treating an aneurysm or the like, which causes little invasion, attention has been recently attracted to vascular embolization in which an embolizing material is deposited within a dilatation. Reference may be made to, for example, U.S. Pat. Nos. 4,884,579 and 4,739,768. In this vascular embolization, the embolizing material deposited within the aneurysm serves as a physical obstacle to a blood stream and can facilitate the formation of thrombus to reduce the risk of aneurysmal rupture.
As the embolizing material to be deposited at an intended site in the vasculature, coiled embolizing materials have been known.
Such a coiled embolizing material is introduced into an aneurysm through a suitable catheter by means of a wire-made push-out device or a guide detachably connected to an end thereof. Reference may be made to, for example, Japanese Patent Application Laid-Open (KOHYO) Nos. 500322/1993, 501015/1996 and 502674/1995 (through PCT route)
More specifically, the coiled embolizing material, to which the push-out device has been connected, is inserted into the catheter, which has been inserted into the vital body in advance in such a manner that its distal opening is sited within the aneurysm, with the coiled embolizing material in the lead. As a result, the embolizing material is transferred through the catheter while being pushed by the push-out device, whereby it is pushed out of the distal opening of the catheter into the dilatation. At the time the whole length of the embolizing material has been pushed out of the distal opening, namely, its joint with the push-out device has reached the distal opening, the push-out device is detached from the embolizing material making good use of a mechanical means, electrolysis or the like, whereby only the embolizing material is deposited within the aneurysm.
FIG. 1 illustrates a conventional coiled body making up a coiled embolizing material.
This coiled body 1 is a helical double-coiled body having deformability. A semi-spherical tip 2 is formed at one end thereof.
Since the coiled body 1 has deformability, it shows a state that it is stretched in a substantially straight line along a catheter when it is pushed by a push-out device to move through the catheter, and returns to the original double-coiled body (the shape illustrated in FIG. 1) when it is pushed out of the catheter into an aneurysm, and the push-out device is detached from the coiled body.
By the way, in order to surely embolize the interior of an aneurysm, it is important to deposit the coiled embolizing material within the aneurysm so as to fit it to the inner wall of the aneurysm.
Therefore, the outer diameter of the coiled body making up the embolizing material (for example, the outer diameter of the double-coiled body illustrated in FIG. 1) must be generally made somewhat greater than the inner diameter (the inner diameter when an internal space of the aneurysm is regarded as a sphere) of the aneurysm in which the coiled body should be deposited.
When the outer diameter of the coiled body making up the embolizing material is greater than the inner diameter of the aneurysm, however, there is a problem that an end portion of the coiled body is extended out of the dilatation.
More specifically, as illustrated in FIG. 2A, in some cases, a distal end portion 5A of a coiled body 5, which has been pushed out of a distal opening of a catheter 3 into an aneurysm 4, may extend out of the opening of the aneurysm 4 into a parental blood vessel 6 outside the dilatation.
Besides, as illustrated in FIG. 2B, in some cases, a proximal end portion 5B of the coiled body 5 deposited within the aneurysm 4 after a push-out device (not illustrated) is detached, may extend out of the opening of the aneurysm 4 into the parental blood vessel 6 outside the dilatation.
Such a state as described above particularly tends to occur when an aneurysm to be embolized has a slender form. When the distal or proximal end portion of the coiled body extends out of the dilatation, a thrombus is formed on the end portion of the coiled body extended out of the dilatation, and so the parental blood vessel is occluded by the thrombus, or the thrombus transmigrates to a peripheral vessel, thereby occluding such a peripheral vessel.